Bratislav Dzombic

Bratislav Dzombic

  • Joined: September 16, 2024
  • Articles: 100

What is energy? The most important thing in physics that nobody can point to

Illustrated featured image about energy showing a scientist examining the Sun, a battery, a kettle, a moving object, and an atom as different expressions of energy.

Energy powers stars, batteries, bodies, power grids, and basically everything that changes. But ask physics what energy actually is, and the answer gets strange fast. Energy is not a substance, not a force, and not simply “the ability to do work.” It is something deeper: a measurable property of physical systems, a conserved quantity tied to the structure of time itself—and, at the frontiers of physics, a concept whose full meaning is still surprisingly unsettled.

What is an electrolyzer? The machine that turns electricity into hydrogen

Electrolyzer featured image showing renewable electricity splitting water into hydrogen and oxygen inside an industrial electrolysis unit.

An electrolyzer takes electricity, water, and some very deliberate electrochemistry and produces hydrogen and oxygen. That sounds simple enough. The interesting part begins when the machine becomes hundreds of megawatts large, starts following wind and solar production, competes for cheap electricity, needs purified water and compression, and discovers that making hydrogen cheaply is mostly an electricity problem wearing a chemistry badge.

What is waste heat? The energy we already paid for and then threw away

Waste heat featured image showing captured industrial heat flowing from a factory toward buildings, heating systems, and a greenhouse.

Factories, power plants, engines, data centers, furnaces, compressors, and even supermarket refrigerators constantly reject heat into the environment. Some of that loss is unavoidable. Some is simply energy leaving the system before we found another useful job for it. Waste heat recovery asks an almost embarrassingly sensible question: if we already paid to create that energy, can we use it again before letting it escape?

What is energy arbitrage? Buying electricity when nobody wants it

Energy arbitrage featured image showing batteries moving cheap daytime electricity toward a higher-value nighttime market.

Electricity can be worth €20/MWh at noon and €150/MWh a few hours later. Energy arbitrage turns that difference into a business model: buy or store electricity when it is cheap, then sell it when it becomes valuable. The idea sounds suspiciously like “buy low, sell high.” It is. The interesting part is what batteries, efficiency losses, degradation, forecasts, negative prices, and thousands of competing batteries do to that beautifully simple plan.

What is black start? How do you restart a grid with no electricity?

Black start featured image showing a hydroelectric plant energizing transmission lines toward a city during power-system restoration.

A blackout creates a wonderfully circular problem: the grid needs power plants to restart, but many power plants need electricity from the grid before they can start. Black start is how operators break that loop—using specially capable resources to create the first energized islands, start larger generators, reconnect transmission lines and loads, synchronize those islands, and gradually rebuild an entire power system from darkness.

What is thermal energy storage? The battery that stores heat instead of electricity

Thermal energy storage tank charged by solar-powered heat pump during the day and supplying home heating after sunset.

Battery storage gets most of the attention, but many energy problems do not actually require electricity to be stored as electricity. If the final job is heating a building, cooling a supermarket, supplying industrial heat, or keeping a district-heating network warm, it may be simpler to store the thermal energy itself. Thermal energy storage can be as basic as a tank of hot water—or as exotic as molten salt, underground reservoirs, ice, phase-change materials, and reversible chemical reactions.